1. Field of the Invention
The present invention relates to a method and apparatus for preparing a map data with regional properties, and more particularly to a method and apparatus that facilitates the preparation of map information that indicates the regional characteristics and properties of regions and points on the map.
2. Description of the Prior Art
Until now, maps have been used in various ways to indicate information graphically. Maps, presented in color have been widely used to indicate the properties of regions and spots wherein individual colors correspond to a particular property or characteristic. Such color maps include maps that show land-use conditions of fields, residential areas, industrial areas, and the like wherein the properties of the land are indicated by respective colors; regional maps of a nationwide census that illustrate different region in different colors; soil maps that depict different geological features in different colors administrative-district maps that show urban and rural prefectures, as well as cities, towns and villages in different colors; and, charts or maps that depict public utility systems for electricity, water supply, sanitation, and the like. These maps are widely used by local government as control data, and by school systems as educational material.
It is advantageous to store such map data in computers, because map information can then be updated relatively easily. Further, storing map data on computer also makes it possible to create new maps by overlapping maps that show different types of information for the same geographical area. For example, a map prepared by superimposing a regional map for planned road construction over a soil map is convenient for checking the soil conditions prior to beginning construction. Further, maps that contain the same type of information can be used to numerically grasp the degree of, say, environmental contamination and improvements thereof in a given area provided that the measurement results on the maps being superimposed were obtained at different times.
In one conventional used to store map information into a computer, the input terminal of a digitizer is first manually passed along the edges of a graphical form (which shows blocks and spots on an original map). In this way, motion data read by the input terminal is stored in the computer as plane data that outlines graphical forms for the various regions and points.
However, even when land-use maps of Japan's relatively small prefectures, (such as Okinawa and Tottori) are prepared on a scale of 1/25000, approximately 100,000 pieces of plane data are required. Since this plane data is manually input using the digitizer as described above, preparation of the data requires an enormous amount of time and labor.
Moreover, in order to assign properties corresponding to the plane data thus input for each individual region and point through computer processing, each item of plane data must form a closed plane. If the boundary (outline) obtained by the plane data is interrupted, the properties corresponding to this plane data flow out of such interrupted point to the periphery. On the other hand, even if an operator feels that the outline of the plane data displayed on a computer screen is continuous, the computer in fact often registers a discontinuity in the data. Consequently, the operator must be extremely careful when manually inputting plane data using the above mentioned digitizer technique, taking care to avoid the generation of discontinuities. As a result, such inputting operations require highly-skilled operators and sophisticated procedures.
For the above reasons, it is said that a 50% to 90% of the preparation costs of map information are allotted to manual labor. And because maps prepared in this way are very expensive, the wide application of map information to various fields is economically difficult.
In addition, since it may take as much as several months to complete the plane data, when used as control data, such plane data tends to be outdated.
For contour maps as widely used in civil engineering and surveying, there is a conventional apparatus for automatically compensating for distortions in graphical forms. The method works picking up the original map data, such as that used for topographical maps through an image scanner, and then storing the graphical form data in a computer. With this system, it is possible to update graphical form data relatively easily using manual input operations. However, with this apparatus, there is no concept of the above-mentioned plane data applied to the graphic data to be processed. Consequently the graphical form data is processed as vector data which merely represents lines. Another drawback of this system is that it does not allow one to automatically detect points discontinuity. In addition, if houses and roads are individually recognized after the graphical form data thus stored are transformed into vector data, and further if an object to be recognized through such vector data classification is, for example, a pair of adjacent houses, each of which is hexagonal in shape, it is impossible to identify one of the adjacent houses because the outline of the house cannot be divided into six items of line data and such items cannot be automatically transformed into vector data so as to combine as a single polygon. In this case, it is necessary for the conventional apparatus to prepare a traced drawing in which the pieces adjacent to each other are previously removed. Doing so entails much time and labor.
As described above, the prior art does not provide for method or apparatus for preparing map information from original maps precisely or automatically.